It looks like some of the images and script references on the page are using http:// instead of https://. That might be causing the form to fail.
You may also try changing this line in the htaccess:
RewriteRule ^(.*)$ https://preferred-cell-systems.com/$1 [R,L]
to:
RewriteRule ^(.*)$ https://preferred-cell-systems.com/$1 [R,P]